A variety of systems are known for regulating the temperature of a liquid, such as oil, using a heat exchanger or an oil cooler. In particular, it is known that one can regulate the temperature of oil used in a transmission with the objective of maintaining the temperature of the oil within a desirable temperature range so the temperature of the oil is neither too hot nor too cold. In one particular system for regulating the temperature of transmission oil by means of a heat exchanger, a mixing valve is provided which is able to direct either hot coolant from a vehicle engine, for example, or cold coolant flowing from a radiator, for example, through the heat exchanger so that the heat exchanger works as a heater or as a cooler. A form of mixing valve for regulating the temperature of a liquid such as coolant includes a valve housing having first and second chambers formed therein as well as inlet and outlet ports for the flow of a liquid into and out of the first chamber. Further ports are provided in the housing for the flow of coolant at either an elevated temperature or at a lower temperature into and out of the second chamber. A linear actuator in the form of a wax motor is mounted in the first chamber and has an actuator body which contains the wax and a piston movable to an extended position by expansion of the wax when the temperature of the wax is increased to a predetermined level. Since a substantial portion of the actuator body is located in the first chamber, the temperature of the actuator body and its wax is determined to some extent at least by the temperature of the liquid flowing through the first chamber. A valve mechanism including a valve spool is operable by the linear actuator with one end of the spool being operably connected to the piston for movement therewith. The valve mechanism is located in the second chamber of the housing and is capable of controlling the flow of both coolant at the elevated temperature and coolant at the lower temperature through the second chamber.
One difficulty with the aforementioned mixing valve is that it requires a number of separate components or parts mounted within the valve housing for the purpose of mounting the linear actuator. In addition, such a mixing valve can be difficult to assemble due to its complexity and can increase manufacturing costs.
Another difficulty with this aforementioned mixing valve is that it is possible for the temperature of the wax in the wax motor actuator to be influenced by not only the temperature of the liquid flowing through the first chamber but also the temperature of the coolant in the second chamber since one end of the wax motor actuator and its piston is either adjacent to or in the second chamber. The influence of the temperature of the coolant can at least in some cases adversely affect the proper operation of the wax motor actuator.
A further difficulty with the aforementioned mixing valve is the pressure drop that can occur in the second chamber, where the coolant pressure can drop using the valve mechanism as described above. The pressure drop can also affect the valve causing leakage.
Therefore, there is a need in the art for a valve apparatus that requires less components and has a simpler design, which can reduce complexity and cost of manufacturing. In addition, there is a need in the art for a valve apparatus that can mitigate against one fluid in a first chamber from contaminating a second fluid in a second chamber. Moreover, there is a need in the art for a valve apparatus that can reduce pressure drops in the second chamber, where a valve mechanism controls the ports through which fluid can flow.